1. Technical Field
The present teaching relates to method and system for batteries. More specifically, the present teaching relates to method and system for a battery charger and systems incorporating the same.
2. Discussion of Technical Background
With the advancement of electronics, portable devices are ubiquitous. As commonly known, such portable devices usually operate on power provided by a battery. Much effort has been spent in prolonging the usage time of a battery. One phenomenon commonly encountered by users of a portable device is that when the battery voltage is below a minimum usable system level, even when the device is connected to an external power source, the “instant-on” function of the device is not possible. In those situations, a user of the device has to wait for the battery to charge to a minimum battery voltage before the device shows any response to the input power. This introduces much inconvenience and inefficiency.
FIG. 1 (PRIOR ART) depicts a conventional battery charger 100 to charge a battery 160. The conventional battery charger 100 comprises a duty cycle generator 130, an input current limit control system 110, a step-down switching regulator 120, a constant charge current amplifier 140, and a constant battery voltage amplifier 150. In this charger, the duty cycle generator 130 is controlled by the input current limit control system 110, the constant charge current amplifier 140, and the constant battery voltage amplifier 150. The duty cycle of the charger 100 controls the step-down switching regulator 120, which subsequently controls the system power to the portable device.
The duty cycle of the charger 100 is dynamically adjusted based on feedback information from multiple sources. For instance, the constant charge current amplifier 140 measures the current that flows through the battery 160 and attempts to control the duty cycle so that the current flowing through battery 160 remains constant. In addition, the constant battery voltage amplifier 150 measures the voltage of the battery 160 and uses such information to control the duty cycle so that the battery voltage remains constant. Furthermore, the input current limit control system 110 measures the input current and uses that information to automatically control the duty cycle generated by the duty cycle generator 130.
The term “lower deck” refers to a minimum voltage that a battery charger produces at its output when the battery is deeply discharged. In this illustrated battery charger, when the battery voltage is lower than the lower deck, there will be no system power sent to the portable device because all the power is channeled to the battery by the battery charger 100. Therefore, it has the problem discussed above with respect to the prior art solutions for battery chargers.